The invention concerns a method and signal conversion device for avoiding undesirable noise in the start up of an amplifying device, as well as to an amplifying device including such a signal conversion device. The signal conversion device (12) comprises a variable gain providing unit (Q3, Q4, Q5, Q6), a voltage to current converter (Q1, Q2, R1, R2), a variable gain control unit (22) controlling the variable gain of the variable gain providing unit, and a bias current control unit (20) for controlling a first biasing current (IB1) of the voltage to current converter, for avoiding DC offset originating noise as well as noise originating from components of the signal conversion device.